title: Thermal stability of anthocyanin extract of Hibiscus sabdariffa L. in the presence of beta-cyclodextrin.
abstract: The thermal stability of anthocyanin extract isolated from the dry calyces of Hibiscus sabdariffa L. was studied over the temperature range 60-90 degrees C in aqueous solutions in the presence or absence of beta-cyclodextrin (beta-CD). The results indicated that the thermal degradation of anthocyanins followed first-order reaction kinetics. The temperature-dependent degradation was adequately modeled by the Arrhenius equation, and the activation energy for the degradation of H. sabdariffa L. anthocyanins during heating was found to be approximately 54 kJ/mol. In the presence of beta-CD, anthocyanins degraded at a decreased rate, evidently due to their complexation with beta-CD, having the same activation energy. The formation of complexes in solution was confirmed by nuclear magnetic resonance studies of beta-CD solutions in the presence of the extract. Moreover, differential scanning calorimetry revealed that the inclusion complex of H. sabdariffa L. extract with beta-CD in the solid state was more stable against oxidation as compared to the free extract, as the complex remained intact at temperatures 100-250 degrees C where the free extract was oxidized. The results obtained clearly indicated that the presence of beta-CD improved the thermal stability of nutraceutical antioxidants present in H. sabdariffa L. extract, both in solution and in solid state.
authors.affiliation: Laboratory of Chemistry-Biochemistry-Physical Chemistry of Foods, Department of Nutrition & Dietetics, Harokopio University, Kallithea, 17671 Athens, Greece.
authors.forename: Ioannis
authors.initials: I
authors.lastname: Mourtzinos
authors.forename: Dimitris P
authors.initials: DP
authors.lastname: Makris
authors.forename: Konstantina
authors.initials: K
authors.lastname: Yannakopoulou
authors.forename: Nick
authors.initials: N
authors.lastname: Kalogeropoulos
authors.forename: Iliana
authors.initials: I
authors.lastname: Michali
authors.forename: Vaios T
authors.initials: VT
authors.lastname: Karathanos
mesh_terms: D000872:Anthocyanins / Q000737:chemistry*; D031584:Hibiscus / Q000737:chemistry*; D006358:Hot Temperature; D007700:Kinetics; D010084:Oxidation-Reduction; D010936:Plant Extracts / Q000737:chemistry*; D047392:beta-Cyclodextrins / Q000737:chemistry*
chemical_list: D000872:Anthocyanins; D010936:Plant Extracts; D047392:beta-Cyclodextrins; C031215:betadex